(CNN)I am just back from South Sudan, one of the world's most fragile nations. For years, I have been moved by the kind people who maintain hope that they will live to see peace. My heart has ached for them, as they have endured pain and violence that make such hope feel out of reach.

Recently, the United Nations declared famine in parts of South Sudan. This was a long time in the making -- the civil war that began in 2013 continues to cause chaos, cutting people off from their land, livelihoods and even the aid they are forced to rely on. To date, famine has put 100,000 people at risk of death, and 7.5 million more need immediate humanitarian assistance.

Forest Whitaker

Every day the conflict continues, South Sudanese people face tremendous risks and unthinkable decisions. With a quarter of the country's population uprooted by violence, stories of rape and torture echo throughout the country. A generation has been robbed of its future by forced recruitment to fight, being mistaken and targeted as opposition fighters and early marriage -- when parents have no other means to pay for necessities like food.

Schools lay destroyed or occupied by armed groups, leaving children unable to fulfill their potential; families are forced to scavenge in swamps to survive.

The international community has ignored countless warnings that South Sudan is on the brink of a genocide. This is a manmade disaster, which means we could have prevented it -- and if we work together now, we can still stop this crisis and save lives.

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People are dying and need urgent action before the situation gets worse. Humanitarian organizations must be able to provide immediate life-saving aid and support for people to start anew. And the impending rainy season will make reaching vulnerable people even more difficult, as rivers flood and roads become impassable.

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Organizations like Oxfam are responding alongside local partners and need our support so they can broaden their response to assist people now before the rains begin. In short, this is a race against time. Without these critical efforts, millions more could be facing famine.

This early test is the time for decisive moral leadership from President Donald Trump and his administration. My hope is that they, along with world leaders, help ensure millions of poor and vulnerable people can survive and ultimately thrive. This is not a political issue, but a human one.

While the leaders of South Sudan have the primary responsibility to protect their own people, the global community has an ethical obligation to step up when lives are on the line. Leaders and donors should fully fund the humanitarian response now.

Forest Whitaker conducting a training for youth leaders in conflict resolution in South Sudan.

The UN has requested $1.6 billion to provide life-saving support to 5.8 million people. That amounts to just $275 to reach each person in need. We must provide food, clean water and other urgent necessities -- and we must also end the conflict, so millions can safely return to homes, schools and work, feeling that their hope was warranted.

Our leaders must hear us speaking on behalf of our brothers and sisters in South Sudan. If the moral duty to save lives and work toward peace is not compelling enough to drive decision-makers, we must remind them that we care and will hold them accountable. It rests in the hands of the common person, as well as those with the power to shape humanity's course toward a world where every child, woman and man's most basic needs are met.

While it's easy for South Sudan to feel distant, the situation is all too real for the South Sudanese mothers choosing which child gets to eat tomorrow. This is a time when we must look outward together and declare that humanity has no borders -- no one deserves to suffer like this, especially in a world of such abundance.

I have met people in South Sudan who are just like you and me, and even in these dark circumstances, they are brimming with hope. In some cases, it's all they have. We must hear them.

For my part, I work to cultivate young people, who are the seeds for a better future in South Sudan, through my foundation, the Whitaker Peace & Development Initiative. We provide promising and talented young women and men with skills and resources that they put to use in their communities as mediators and entrepreneurs.

Their dedication to peace is impressive and I cannot doubt that, with time, the small miracles they accomplish in their communities will have ripple effects. But they know they cannot succeed all alone.

If we unify our voices and respond to this urgent call, the hope of the people of South Sudan can grow into the beautiful and rich future that they deserve.